German Laid-open Specification DE 10 2004 056 932 A1 discloses a cup made of paper material having a partially conical tubular wall and a bottom wall joined thereto in a substantially liquid-tight manner. The cup comprises, above its bottom wall, a peripheral deforming entity that is in the form of a so-called “stacking shoulder” and that is provided for the purpose of supporting a lower bead of an outer sleeve of the cup above it in a stack containing a plurality of cups. The peripheral deforming entity extends around the periphery of the tubular wall of the inner cup and is formed by pushing an annular plunger around the tubular wall, while the internal surface of the inner cup is abutted by a mandrel. The peripheral deforming entity is incorporated in the inner cup when the latter is in its finished state, that is, a state in which a pot-type bottom wall has already been joined to the conical tubular wall of the inner cup in a liquid-tight manner to form a peripheral edge frame, and a mouth bead has been formed at the top edge of the tubular wall of the inner cup.
European Laid-open Specification EP 1 785 265 A1 discloses a cup of a substantially identical design. When the peripheral stacking shoulder is formed by means of an annular plunger, a mandrel is placed in the interior of the inner cup such that a portion of the mandrel of reduced external periphery is disposed so as to be adjacent to the overlap region. The mandrel disposed inside the inner cup thus has a recess in the overlap region for the purpose of accommodating the double material thickness occurring in the overlap region when the stacking shoulder is formed. This recess enables the stacking shoulder to be shaped uniformly on the external periphery of the inner cup without crushing the material in this region. The peripheral stacking shoulder is incorporated in the inner cup when the latter is in its substantially finished state, that is to say, when it already has a pot-shaped bottom wall joined in a liquid-tight manner to the tubular wall to form a peripheral edge frame, and also has a mouth bead formed at the top edge of the tubular wall.
The overlap region is a critical factor in the case of a more pronounced peripheral stacking shoulder or when use is made of cheap materials or of materials that are less suitable for deformation, and leaks can occur in this overlap region. The method of forming the peripheral stacking shoulder can also result in unwanted material displacements resulting in deformation of the bottom wall of the cup so that the cup no longer stands level.
It is an object of the present invention to provide an improved cup made of paper material and an improved method for the fabrication of such a cup.
According to the invention, a cup made of paper material is provided for this purpose, which cup has a fillable interior comprising a tubular wall that is at least partially conical, and a bottom wall that is joined to the tubular wall at the bottom end of its interior in a substantially liquid-tight manner, wherein the tubular wall is produced from a plane blank, the end regions of which are joined together in an overlap region and wherein the tubular wall delimiting the interior comprises at least one deforming entity extending in the peripheral direction, which peripheral deforming entity is not formed in the overlap region.
By omitting the peripheral deforming entity or the stacking shoulder in the region of the side seam, that is, the region of the overlap, an improved cup made of paper material can be achieved, surprisingly, due to the fact that leaks are avoided in the region of said side seam. This is because no deformation takes place in this overlap region, which thus ensures that the side seam does remain intact and the end regions of the tubular wall in the overlap region do not separate from each other. Very satisfactory stacking properties of the cup of the invention can be achieved in spite of the fact that the peripheral deforming entity is omitted in the overlap region.
In a development of the invention, the peripheral deforming entity extends around the entire periphery of the tubular wall with the exception of the overlap region.
In this way, the peripheral deforming entity can serve as a means for supporting another cup, and very satisfactory stacking properties can be achieved, since the peripheral deforming entity is provided around the entire periphery of the tubular wall with the exception of the overlap region.
In a development of the invention, the peripheral deforming entity follows a curve or bend in the region adjacent to the overlap region, and the peripheral deforming entity, as regarded in the direction toward the overlap region, follows a curve or bend toward the bottom wall of the cup on both sides of the overlap region.
By means of such a bent or curved shape of the peripheral deforming entity on both sides of the overlap region, material stresses occurring due to the special structure of the paper material used for cups can be largely prevented or controlled such that they do not result in irregularly deformed cups. Thus the peripheral deforming entity does not terminate abruptly on reaching the overlap region, but rather it follows a bend or curve directed toward the bottom wall of the cup. The bent or curved shape of the peripheral deforming entity is conducive to the avoidance of regions of excessive deformation in which the paper material might tear.
In a development of the invention, the peripheral deforming entity, as regarded in the direction toward the overlap region, extends in the peripheral direction and then curves downwardly toward the bottom wall through an angle of 90°.
In this way, it is possible to combine satisfactory stacking properties of the peripheral deforming entity, free from deformation at the overlap region, with the prevention of excessive material deformation.
In a development of the invention, the peripheral deforming entity follows a curve forming the arc of a circle.
The peripheral deforming entity following a curve forming the arc of a circle having an angle of curvature of 90° toward the bottom wall is conducive to the prevention of material stresses.
In a development of the invention, the peripheral deforming entity diminishes in radial depth as it approaches the overlap region.
In this way, the depth of the peripheral deforming entity and thus also the necessary material deformation can be gradually diminished as it approaches the overlap. Advantageously, the depth of the peripheral deforming entity diminishes gradually down to zero. In this case, the peripheral deforming entity does not terminate abruptly so that the material near the overlap region is not exposed to excessive stresses or deformation.
In a development of the invention, the inside diameter of the tubular wall at the level of the peripheral deforming entity is smaller than the inside diameter of the tubular wall at the level of the bottom wall.
In this way, excellent stacking properties can be achieved. The peripheral deforming entity or the stacking shoulder then protrudes into the interior to an extent that even makes it possible to compensate for tolerances in the shape of the stacked cup above, that is, for example, in the peripheral edge frame thereof implemented for stacking purposes. Since the overlap region is relieved of such severe deformation, leaks in the overlap region are obviated.
The object of the invention is also achieved by a method for the fabrication of a cup made of paper material, which method includes the following steps: shaping a plane blank to form a substantially conical tubular wall and joining the end regions of the blank to each other in an overlap region, inserting a pot-shaped bottom wall into the conical tubular wall so that the peripheral pot-shaped radial wall of the pot-shaped bottom wall is substantially parallel to the internal surface of the conical tubular wall, and incorporating a peripheral deforming entity in the conical tubular wall excluding the overlap region.
By excluding the overlap region during the process of incorporating the peripheral deforming entity, it is possible to avoid the occurrence of leaks in the overlap region. Advantageously, the process of forming the peripheral deforming entity is carried out before the tubular wall is joined to the pot-shaped radial wall of the bottom wall in a secure and liquid-tight manner to form a peripheral edge frame. Advantageously, the tubular wall is merely wrapped around the bottom edge of the pot-shaped radial wall of the bottom wall without there being a firm joint between the tubular wall and the pot-shaped radial wall of the bottom wall. The process of wrapping the bottom end of the tubular wall is also referred to as the so-called process of rolling the bottom wall and it is typically carried out by moving a groove-shaped plunger toward the bottom edge of the tubular wall. Consequently, the bottom edge is rolled in through 180° and, as a result, that region of the tubular wall which protrudes beyond the bottom edge of the pot-shaped radial wall of the bottom wall is wrapped around the bottom edge of said pot-shaped radial wall. Alternatively, the tubular wall can be joined exclusively to the external surface of the pot-shaped radial wall so that it is then not necessary to wrap the bottom region of the tubular wall. Thus displacement and compression of material resulting from the process of incorporating the peripheral deforming entity with the omission of the overlap region can be compensated before the tubular wall is joined to the bottom wall in a secure and liquid-tight manner. The omission of the overlap region when forming the peripheral deforming entity or the stacking shoulder results in the occurrence of greater material displacements than occur when forming a deforming entity extending around the entire periphery of the tubular wall. This is, for example, simply due to the fact that the tubular wall decreases in length in those regions where the peripheral deforming entity is formed, but maintains its original length in regions where the peripheral deforming entity is not formed, that is, in the overlap region. Such increased material displacements can result in paper cups that are not shaped uniformly and that therefore might suffer from problems relating to their leak tightness and are especially considered by users as being lopsided and inferior. Surprisingly, it is possible, by means of the present invention, to compensate for these increased material displacements occurring when the peripheral deforming entity is formed with the omission of the overlap region by forming the peripheral deforming entity before the tubular wall has been securely joined to the bottom wall in a liquid-tight manner.
In a development of the invention, the process of wrapping the bottom region of the conical tubular wall around the pot-shaped radial wall and the method of forming the peripheral deforming entity are carried out essentially simultaneously.
For example, the process of wrapping the bottom region of the conical tubular wall or the process of rolling the bottom wall can be carried out by moving a groove-shaped plunger toward the bottom end of the tubular wall. The plunger, as regarded in the direction toward the cup, comprises a peripheral ring that is then moved toward the tubular wall from the outside and that shapes the peripheral deforming entity whilst excluding the overlap region. The process of forming the peripheral deforming entity can be carried out by axially moving the ring toward the conical tubular wall, but it may also be carried out, for example, by moving a plurality of plungers in the radial direction towards the conical tubular wall. At all events, the ring or the plunger are designed such that the overlap region is excluded and no peripheral deforming entity or stacking shoulder is formed in said overlap region.
In a development of the invention, the processes of wrapping the bottom region of the conical tubular wall and of forming the peripheral deforming entity are carried out by pushing a plunger over the bottom region of the conical tubular wall in a direction that is parallel to the longitudinal center axis of the conical tubular wall.
The process of pushing the plunger axially parallel to the longitudinal center axis also enables peripheral deforming entities protruding by a comparatively large distance into the interior to be reliably formed without resulting in any damage to the paper material. In particular, the paper material of the tubular wall will not be stretched during such a procedure, but is, rather, folded down more or less inwardly, and the height of the cup between the peripheral deforming entity and the bottom edge of the cup is reduced at the same time as the peripheral deforming entity is formed. As mentioned above, this reduction in height, as regarded over the periphery of the cup, is carried out unevenly since the overlap region is excluded. The resulting material displacements within the tubular wall can thus be compensated for in that the process of rolling the bottom wall or wrapping the tubular wall is carried out at the same time as the process of forming the peripheral deforming entity, whilst the process of forming the peripheral edge frame, by means of which the tubular wall is then securely joined in a liquid-tight manner to the pot-shaped radial wall of the bottom wall is not carried out before the peripheral deforming entity has been formed.
In a development of the invention, the process of pressing the pot-shaped radial wall of the bottom wall and the conical tubular wall together in a liquid-tight manner is carried out after the step of forming the peripheral deforming entity.
The object of the invention is also achieved by a device for carrying out the method of the invention, which device comprises a mandrel and a plunger for incorporating a peripheral deforming entity in a conical tubular wall of a cup made of paper material, with the mandrel comprising a step or heel extending in the peripheral direction and the plunger comprising an annular portion for shaping the peripheral deforming entity, wherein the step or heel is discontinued in the overlap region in the tubular wall and/or the annular portion of the plunger is recessed in the overlap region of the tubular wall.
The provision of the discontinued step on the core mandrel in the overlap region reduces the risk of the paper material becoming wrinkled in this region, that is, at the level of the peripheral deforming entity to be formed and in the region of the side seam or overlap.
Additional features and advantages of the invention are revealed in the claims and in the following description of preferred embodiments of the invention, with reference to the drawings. Individual features of the different embodiments shown can be arbitrarily combined with each other, as required, without going beyond the scope of the present invention.